Valve assembly for gas generating system

ABSTRACT

A gas generating system includes a housing having a passage and a forcing member positioned in the passage. A flowable material is positioned in the passage to resist motion of the forcing member. The housing is configured to enable a flow of flowable material out of the housing responsive only to a motion of the forcing member.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of prior application Ser. No.12/217,646, filed on Jul. 7, 2008 now U.S. Pat. No. 7,857,345, whichclaims the benefit of provisional application Ser. No. 60/958,510 filedon Jul. 6, 2007.

BACKGROUND OF THE INVENTION

The present invention relates generally to gas generating systemsincorporating mechanisms for regulating a flow of gas from the system.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings illustrating embodiments of the present invention:

FIGS. 1-10 show the structure and operation of a gas generating systemincorporating a valve assembly in accordance with a first embodiment ofthe present invention.

FIGS. 11-14 show the structure and operation of a valve assembly inaccordance with a second embodiment of the present invention.

FIG. 15 is a schematic view of an airbag system and a vehicle occupantprotection system incorporating a gas generating system including avalve assembly in accordance with embodiments of the present invention.

SUMMARY OF THE INVENTION

In one aspect of the embodiments of the present invention, a gasgenerating system is provided including a housing having a passage, anda forcing member positioned in the passage. A flowable material ispositioned in the passage to resist motion of the forcing member. Thehousing is configured to enable a flow of flowable material out of thehousing responsive only to a motion of the forcing member.

DETAILED DESCRIPTION

FIGS. 1-10 show the structure and operation of embodiments of a gasgenerating system 8 incorporating a valve assembly 10 for moderating orattenuating a release of fluid from a container upon activation of thegas generating system. Referring to FIGS. 1-2, valve assembly 10 isshown secured to a gas source, such as a gas bottle or tank 18 in whicha fluid (in this case, an inflation gas) is stored. Bottle 18 has anannular wall 36 with an edge 26 defining a bottle opening 24.

A rupturable membrane 22 (for example, a burst disk) is secured in fluidcommunication with an interior of bottle 18. Membrane 22 forms afluid-tight barrier preventing flow of gas through or around themembrane. In the embodiment shown in FIGS. 1-2, membrane 22 is seatedalong an edge of an opening 13 formed in a housing 12 (described ingreater detail below) containing the elements of the valve assembly.Membrane 22 is welded or otherwise secured over opening 13 to obstructflow of the fluid during normal vehicular operation.

Membrane 22 may be stamped or formed from any of various disks, foils,films, etc., as is known in the art. The materials and structure of themembrane will depend on the pressure range in which the membrane isintended to rupture, the desired performance characteristics of gasgenerating system 8, and other factors. For example, disks made frommaterials and/or having structures which are relatively more or lessreadily ruptured may be used.

Housing 12 defines a passage 11 for receiving the fluid therethrough andterminating in an endwall 52. Housing 12 is coupled to the gas source soas to enable fluid communication between the gas source and passage 11.Passage 11 is dimensioned so as to support and enable movement of aforcing member 40 (described below) therealong, in response to pressurefrom a flow of gas emanating from bottle 18 upon activation of the gasgenerating system.

An opening 53 is formed endwall 52 to provide egress for a flowablematerial 51 stored in a passage second portion or cavity 49 (describedbelow) formed between forcing member 40 and endwall 52. A tape seal orother known seal (not shown) may be secured over opening 53 and isstructured to open or otherwise fail under pressure exerted by flowablematerial 51, thereby enabling the flowable material to flow throughopening 53 as forcing member 40 exerts pressure on the flowablematerial. The seal may be similar to membrane 22 previously described.

A plurality of gas discharge orifices 54 is formed in the housing toenable fluid communication between an interior of the housing and anexterior of the housing. The embodiment shown in FIGS. 1-2 includes fourgas discharge orifices 54 substantially evenly spaced about thecircumference of an end of the housing. Housing 12 may be cast,machined, or otherwise formed from a metal, metal alloy, or othersuitable material.

The housing may incorporate a filter (not shown) therein to filtercombustion products from the inflation fluid prior to gas distribution.Any suitable metallic mesh filter or woven wire cloth may be used, manyexamples of which are known and obtainable from commercially availablesources (for example, Wayne Wire Cloth Products, Inc. of BloomfieldHills, Mich.) Housing 12 is fabricated (for example, by machining,casting, or some other suitable process) from a rigid material such ascarbon steel or stainless steel. Other suitable types or designs offilters may also be used.

Forcing member 40 is positioned within passage 11 so as to slidably movealong the passage under the influence of gas from the gas source. A seal42 (for example, an O-ring seal) is secured along an outer surface ofthe forcing member (for example, in a groove as shown in FIG. 2) so asto seal the interface between forcing member 40 and the housing interiorwall.

In the embodiments shown in FIGS. 1-10, forcing member 40 and seal 42divide passage 11 into a first portion or cavity 49 and a second portion11 b. Seal 42 is structured to prevent the flow of flowable material 51(described below) from cavity 49 between housing 12 and forcing member40. Seal 42 is also structured to prevent flow of flowable material outof passage first portion 49, to passage second portion 11 b, both priorto and during deployment of the gas generating system. In the embodimentshown in FIGS. 1-10, the flow of gas is in direction “A” and seal 42 isdesigned to prevent a flow of flowable material in a direction “B”substantially opposite direction “A”. In the embodiment shown in FIGS.1-10, seal 42 is configured to slide freely within passage 11 along thehousing interior wall, in conjunction with forcing member 40. In analternative embodiment (not shown), the seal 42 is secured along a wallof housing 12 or is otherwise secured within the housing such that theseal does not move in conjunction with the forcing member. Variousalternative types of seals or gaskets may be employed provided thealternative seals form a suitable seal that is forcing in conjunctionwith forcing member 40.

Forcing member 40 may be cast, stamped, extruded, or otherwisemetal-formed. Alternatively, forcing member 40 may be molded from asuitable high-temperature resistant polymer or otherwise formed fromanother suitable material. In a particular embodiment, the design offorcing member 40 and the material from which the forcing member isformed are selected to minimize the mass of the forcing member. It isbelieved that this reduces the static and dynamic inertia of the forcingmember during actuation, thereby enhancing the responsiveness of thevalve assembly described herein. Conversely, a forcing member having arelatively greater mass may be provided to delay or attenuate motion ofthe forcing member responsive to the increased pressure within thehousing, thereby affecting the rate at which orifices 54 open (asdescribed below) and, consequently, affecting the inflation profile of agas-actuatable device operatively coupled to the gas generating system.In another particular embodiment, the forcing member is formed from athermally conductive material and has a relatively small dimension inthe direction of flow of gas, or is otherwise structured so as tofacilitate rapid conduction of heat from the gas through the forcingmember to the flowable material.

The flowable material 51 is positioned in the cavity 49 to resist motionof forcing member 40 in the direction indicated by arrow “A” (see FIG.2). The flowable material 51 in cavity 49 may be any material (forexample, a gas, liquid, gelatinous substance, powder, etc.) containablein the cavity and capable of flowing out of endwall opening 53 underpressure exerted by forcing member 40. As used herein the term “flowablematerial” is understood to mean a substance that at least partiallyconforms to the shape of a container or confinement in which thesubstance is placed after being placed in the confinement, and that iscapable of flowing.

The composition and other characteristics of the flowable material maybe specified such that the material, either alone, in conjunction with,or in response to other features or operating parameters of the system,facilitates the attainment of a desired inflation profile of agas-actuated device operatively coupled to the gas generating system.For example, a shear-thinning material such as a pseudoplastic material,a thixotropic material, or a Bingham Plastic material may be specified.As used herein, a pseudoplastic material is defined as a material whoseviscosity decreases relatively rapidly under an applied shear stress andthen remains relatively constant under continued application of thestress. As used herein, a thixotropic material is defined as a materialwhose viscosity decreases under an applied shear stress and thencontinues to decrease under continued application of the stress. As usedherein, a Bingham plastic material is defined as a material whoseviscosity decreases only after a shear stress applied to the materialexceeds a minimum predetermined yield value.

In one example, where a pseudoplastic material is used for the flowablematerial, it is believed that a forcing member pushing against theflowable material in response to gas pressure would exhibit a relativelyrapid initial movement in direction “A” corresponding to an initialdecrease in material viscosity, breakage of any seal positioned overopening 53, and initial flow of the flowable material out of opening 53.After this initial motion, it is believed that motion of the forcingmember in response to the gas pressure would be relatively slower andrelatively constant. In the manner described below, gas exit opening(s)will open in correspondence with this motion of the forcing member,thereby producing a corresponding inflation profile in an inflatabledevice coupled to the gas generating system. In such a manner, thecharacteristics of the flowable material influence the gas generatingsystem inflation profile.

In a particular embodiment of the invention, the viscosity of theflowable material 51 varies inversely with its temperature, and heat isconducted through the forcing member to elevate the temperature of theflowable material in the cavity, thereby reducing its viscosity.Alternatively, a flowable material may be specified which exhibitsrelatively little change in viscosity under pressure and/or over thetemperature range experienced by the interior of housing 12 duringoperation of the gas generating system. By affecting the viscosity ofthe flowable material, the ease with which the material will flow out ofopening 53 is correspondingly affected. Thus, by appropriatespecification of the flowable material, the resistance to movement offorcing member 40 and, consequently, the speed at which openings 54 areuncovered may be controlled as desired. Examples of flowable materialssuitable for use in the embodiments of the present invention are KE1052or X832 curable silicone gels manufactured by Shin-Etsu Silicones ofAmerica, of Akron, Ohio.

Referring to FIG. 1A, in another particular embodiment of the invention,the flowable material does not occupy the entire volume of passage firstportion 49. That is, the passage first portion or cavity 49 has a firstvolume V1 prior to activation of the gas generating system, and theflowable material 51 occupies a second volume V2 that is less than thefirst volume.

It will be appreciated that design considerations such as the bottleinternal fluid pressure, the tightness of the seal between the forcingmember and housing wall 15, the area of the forcing member acted upon bythe released gas, the size of opening 53, the mass of forcing member 40,the viscosity, composition, compressibility, and other characteristicsof the flowable material in cavity 49, the temperature of the gasflowing through passage 11, the amount of flowable material in cavity49, the number, sizes, and arrangement of openings 54, the distance thatthe forcing member must travel in order to uncover the gas exitopenings, and other parameters may be iteratively harmonized to providea total open area of gas exit orifices 54 which gradually increases at apredetermined rate upon activation of the gas generating system, therebycorrespondingly achieving a desired initial rate of gas release fromhousing 12. As such, when properly informed with system performancerequirements and data (typically developed in gas generating systemdesign and manufacture) relating to the interactions between these andother design considerations, the actual dimensions and parameters of thesystem for any particular application may be appropriately anditeratively selected to result in a system that provides an initial gasrelease having a mass and pressure within desired predetermined ranges.In sum, the dimensions of the system elements described above and theeffects of other design variables as known in the art may be eithersingularly or jointly evaluated on a trial and error basis for theireffects on performance characteristics of the gas generating system.

Operation of mechanism 10 will now be discussed.

FIGS. 3-10 are cross-sectional, interior views (FIGS. 2, 4, 6, 8, and10) and respective exterior views (FIGS. 1, 3, 5, 7, and 9) of the valvemechanism, showing operation of the mechanism in progression from thebursting of membrane 22 (FIG. 4) through subsequent movement of forcingmember 40 along passage 11 in direction “A”, as the forcing memberpushes against flowable material 41 to expel the material (as seen inFIGS. 6, 8, and 10) from housing 12.

Referring to FIGS. 3-10, upon a crash event, a signal from a crashsensor or accelerometer (not shown), for example, activates the gasgenerating system. Upon system activation, the pressure of the gasstored in bottle 18 is increased by heating or other means, to burstmembrane 22 (see FIGS. 3 and 4). Alternatively, any of a variety ofother known methods may be employed to burst the membrane. Gasesreleased from bottle 18 then proceed along passage 11 to impinge uponforcing member 40. Under the influence of the released gases, forcingmember 40 moves in the direction of arrow “A”, exerting pressure onflowable material 51 stored in cavity 49. As pressure within cavity 49increases, the tape seal over opening 53 is ruptured, thereby enablingflowable material 51 to flow out of opening 53 under the pressureexerted by forcing member 40.

As forcing member 40 moves along passage 11, the sliding action of theforcing member 40 exposes gas exit orifices 54 to the released gas,thereby permitting release of the gas therethrough. In the embodimentshown in FIGS. 1-10, and as seen in particular in FIGS. 1-2, only arelatively small portion of each of orifices 54 is initially open topermit a flow of gas therethrough. Thus, the flow of gas from passage 11through orifice(s) 54 is partially blocked by forcing member 40 prior toactivation of the gas generating system. As forcing member 40 movesgradually (FIGS. 6, 8, and 10) along passage 11 under the influence ofpressure exerted by fluid from bottle 18, a greater and greater area ofeach orifice 54 is opened to the gas, thereby providing a greater openorifice area through which the gas can flow out of housing 12, andenabling an increased gas flow rate from the housing.

In the embodiment described above, because only a portion of each gasexit orifice 54 (rather than the entire orifice) is opened initially topermit gas flow from housing 12, the initial release of gas from housing12 is attenuated or moderated, thereby reducing the likelihood of damageto an inflatable element (for example, an airbag) operatively coupled tothe gas generating system. The moderated gas flow also reduces thelikelihood of damage to portions of the vehicle and the likelihood ofinjury to passengers resulting from overly aggressive airbag deployment.

Referring to FIGS. 11-14, in an alternative embodiment 108 of the gasgenerating system, forcing member 140 b is formed by a portion of acup-shaped frangible seal 140 which is secured to a-housing 112. Seal140 has a score or slit (not shown) along at least a portion thereof toprovide a predetermined failure region along the seal adjacent anigniter 66 (described below) positioned within, or in fluidcommunication with the interior of, housing 112 for fracturing seal 140.A connecting passage 113 in communication with passage 111 is formed inhousing 112 to enable fluid communication between passage 111 theigniter 66.

Igniter 66 is positioned in relation to housing 112 so as to enablefluid communication with seal 140 upon activation of the gas generatingsystem. In the embodiment shown, igniter 66 is crimped or otherwisesuitably secured to the periphery of housing 112 and extends through awall of the housing so that, upon activation of the igniter, the igniterenters into fluid communication with passage 111 via connecting passage113. It may be seen that igniter 66 is spaced apart from seal 140 and ispositioned such that by-products resulting from activation of theigniter impinge upon the scored or pre-fractured region of seal 140 whenthe igniter is activated. One example of an igniter suitable for theapplication described herein is disclosed in U.S. Pat. No. 6,009,809,incorporated herein by reference. Other igniters mountable so as to bein communication with chamber 20 may also be used.

In the embodiment shown in FIGS. 11-14, which does not include a sealsimilar to seal 42 shown in FIGS. 1-8, the flowable material residing inpassage 111 is a material (for example, a gelatinous material) that doesnot easily flow under the forces to which the material is exposed priorto activation of the gas generating system.

Frangible seal 140 may be formed from any suitable material, such as ametallic material or a polymer. The material from which the seal isformed and/or the structure of the frangible seal should have sufficientstrength and stiffness to prevent deformation of frangible seal forcingmember 140 b into gas exit orifices 54 during operation of the gasgenerating system.

Operation of the embodiment shown in FIGS. 11-14 is substantially thesame as operation of the previously described embodiment. Upon a crashevent, a signal from a crash sensor or accelerometer (not shown)activates igniter 66. By-products resulting from activation of theigniter impinge upon the scored region of seal 140, producing fractureof the seal into a first, static portion 140 a and a second, movingportion 140 b. Moving portion 140 b serves as the forcing member, movingalong passage 111 and compressing a flowable material 151 stored in acavity 149 in the same manner as set forth in the previously describedembodiment.

Alternative methods for fracturing seal 140 may be used. For instance,the methods usable for rupturing seal 22 as previously described mayalso be used to rupture seal 140. For example, the gas pressure insidebottle 18 may be increased by heating the gas in the bottle, through theactivation of an initiator (not shown) in the bottle or by other means.Alternatively, a shock wave can be generated by an initiator or otherdevice positioned spaced apart from the seal. This shock wave travelsthrough the gas generating system to impinge upon the seal, rupturingthe seal. Other methods for rupturing seal 140 are also contemplated.

In a particular embodiment (not shown), a seal similar to seal 42 shownin FIGS. 1-8 is formed along frangible seal 140 for preventing flow offlowable material out of passage 111 in a direction opposite thedirection of travel of forcing member 140 b. The seal may be integrallyformed (as part of the structure of the frangible seal), or thebackflow-preventing seal may be formed from a separate component whichis attached to either a portion of the frangible seal or to the housing.

In another particular embodiment, frangible seal 140 is in contact withflowable material 149 prior to activation of the gas generating system,and need not move along passage to engage the flowable material.

While certain embodiments of the valve assembly are described herein asthey might be employed to regulate flow of fluid from a gas sourcecontaining a stored gas, these embodiments not restricted to suchapplications. Thus, the embodiments described herein may used or adaptedto control the flow of gas from any other suitable gas source. Forexample, any of the embodiments described herein can be adapted andemployed to regulate gas flow from a gas source which generates gaspyrotechnically.

Any embodiment of the gas generating system described herein may beincorporated into an airbag system 200, as seen in FIG. 15. Airbagsystem 200 includes at least one airbag 202 and a gas generating system8, 108 as described herein coupled to airbag 202 so as to enable fluidcommunication with an interior of the airbag. Airbag system 200 may alsoincorporate (or be in operative communication with) a crash event sensor210 including a known crash sensor algorithm that signals actuation ofairbag system 200 via, for example, activation of igniter 66 (not shownin FIG. 15) or activation of a mechanism for increasing the pressurewithin bottle 18 to rupture membrane 22 in the event of a collision.

Referring again to FIG. 15, an embodiment of the gas generating systemor an airbag system including an embodiment of the gas generating systemmay be incorporated into a broader, more comprehensive vehicle occupantrestraint system 180 including additional elements such as a safety beltassembly. Safety belt assembly 150 includes a safety belt housing 152and a safety belt 160 in accordance with the present invention extendingfrom housing 152. A safety belt retractor mechanism 154 (for example, aspring-loaded mechanism) may be coupled to an end portion 153 of thebelt. In addition, a safety belt pretensioner 156 may be coupled to beltretractor mechanism 154 to actuate the retractor mechanism in the eventof a collision. Typical seat belt retractor mechanisms which may be usedin conjunction with the safety belt embodiments of the present inventionare described in U.S. Pat. Nos. 5,743,480, 5,553,803, 5,667,161,5,451,008, 4,558,832 and 4,597,546, incorporated herein by reference.Illustrative examples of typical pretensioners with which the safetybelt embodiments of the present invention may be combined are describedin U.S. Pat. Nos. 6,505,790 and 6,419,177, incorporated herein byreference.

Safety belt system 150 may incorporate (or be in operative communicationwith) a crash event sensor 158 (for example, an inertia sensor or anaccelerometer) including a known crash sensor algorithm that signalsactuation of belt pretensioner 156 via, for example, activation of apyrotechnic igniter (not shown) incorporated into the pretensioner. U.S.Pat. Nos. 6,505,790 and 6,419,177, previously incorporated herein byreference, provide illustrative examples of pretensioners actuated insuch a manner.

It will be understood that the foregoing descriptions of variousembodiments of the present invention is for illustrative purposes only.As such, the various structural and operational features hereindisclosed are susceptible to a number of modifications, none of whichdeparts from the scope of the present invention as defined in theappended claims.

1. A gas generating system comprising: a housing having a passage; aforcing member positioned in the passage; and a flowable materialpositioned in the passage to resist motion of the forcing member,wherein the system is configured to enable a flow of flowable materialout of the housing responsive only to a motion of the forcing member. 2.The gas generating system of claim 1 wherein the flowable material is agas.
 3. The gas generating system of claim 1 wherein the flowablematerial is a powder.
 4. The gas generating system of claim 1 whereinthe flowable material is a liquid.
 5. The gas generating system of claim1 wherein the flowable material is a gelatinous substance.
 6. The gasgenerating system of claim 5 wherein the flowable material comprises acurable silicone gel.
 7. The gas generating system of claim 1 whereinthe flowable material is a thixotropic material.
 8. The gas generatingsystem of claim 1 wherein the flowable material is a Bingham plasticmaterial.
 9. The gas generating system of claim 1 wherein the flowablematerial is a pseudoplastic material.
 10. The gas generating system ofclaim 1 wherein the flowable material is a shear-thinning material. 11.The gas generating system of claim 1 wherein the forcing member at leastpartially blocks a flow of gas from the passage to an exterior of thehousing prior to activation of the gas generating system.
 12. A vehicleoccupant protection system comprising a gas generating system inaccordance with claim
 1. 13. An airbag system comprising including a gasgenerating system in accordance with claim
 1. 14. The gas generatingsystem of claim 1 further comprising: a frangible seal coupled to thehousing and configured to prevent a flow of gas along the passage; andmeans for fracturing the seal to form a first seal portion and a secondseal portion, wherein the means is configured to fracture the seal suchthat the second seal portion comprises the forcing member afterfracturing of the seal.
 15. The gas generating system of claim 14wherein the passage and the forcing member are configured so as toenable the forcing member to move along the passage to contact theflowable material after fracturing of the seal.
 16. A vehicle occupantprotection system including a gas generating system in accordance withclaim
 14. 17. The gas generating system of claim 1 wherein the system isconfigured such that flowable material moves along the passage in afirst direction responsive to motion of the forcing member in the firstdirection.
 18. A vehicle occupant protection system including a gasgenerating system in accordance with claim
 17. 19. A gas generatingsystem comprising: a housing having a passage; a forcing memberpositioned in the passage; and a flowable non-gaseous materialpositioned in the passage to resist motion of the forcing member.